Its the shaft that moves out of the green pot gear.You have to push in a drill bit the same diameter as the shaft to hold all the numbers on it together. As the shaft comes out you rough it up with a smal file so the super glue will stick to it in the pot gear. If you do opt out, and feel the need to fit another speedo head ,you will need one with the same number on the speedo face. Numbers --------VDO make.